Abstract: When substances are developed in the aim to be a constituent of personal care products, and to be applied on the skin, it is necessary to carry out an assessment of potential phototoxic hazard. Phototoxicity is skin reaction caused by concurrent topical or systemic exposure to specific molecule and ultraviolet radiation. Most phototoxic compounds absorb energy particularly from UVA light leading to the generation of activated derivatives which can induce cellular damage. This type of adverse cutaneous response can be reproduced in vitro using different models of phototoxicity such as the validated 3T3 Neutral Red Uptake (NRU) phototoxicity assay. In the present study we utilised two different cell lines (the murine fibroblastic cell line 3T3 and the rabbit cornea derived cell line SIRC) to compare the photo-irritation potential of a strong phototoxic compound, chlorpromazine, to a weaker composite, such as 8-methoxypsoralen and Bergamot oil. After comparison of the different systems, five other essential oils were tested with both cell lines. Cellular damage was evaluated by the NRU cytotoxicity test or by MTT conversion test.

Abstract: BACKGROUND: Macrophages, upon encounter with micro-organisms or stimulated by cytokines, produce various effector molecules aimed at destroying the foreign agents and protecting the organism. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are front line molecules exerting strong cytotoxic activities against micro-organisms and many cells, including macrophages themselves. Using cells of the murine macrophage cell line (RAW 264.7) stimulated in vitro with lipopolysaccharide (LPS) and/or interferon (IFN-gamma), which induce strong endogenous NO production, we examined by which mechanisms a fraction of activated macrophages protect themselves from nitrosative stress and manage to escape destruction? RESULTS: We observed that survivors (10-50% depending on the experiments) had acquired a resistant phenotype being capable to survive when further exposed in vitro to an apoptosis inducing dose of the NO donor compound DETA-NO. These cells expressed an increased steady-state levels of Mn SOD, CuZn SOD and catalase mRNA (130-200%), together with an increased activity of the corresponding enzymes. Intracellular concentration of glutathione was also increased (x 3.5 fold at 6 hours, still maintained x 5.2 fold at 48 hours). Neither mRNA for glutathione peroxydase, gamma-glutamylcysteine synthase and glutathione reductase, nor thioredoxine and thioredoxine reductase, were significantly modified. Additional experiments in which RAW 264.7 cells were stimulated with LPS and/or IFN-gamma in the presence of relatively specific inhibitors of both Mn and Cu/Zn SOD, aminotriazol (ATZ) catalase inhibitor and buthionine sulfoximine (BSO) glutathione inhibitor, showed that inhibiting LPS-induced up-regulation of intracellular redox buffering systems also prevented acquisition of the resistant phenotype. CONCLUSIONS: Our data suggest a direct causal relationship between survival of a fraction of macrophages and a up-regulation of key sets of auto-protective intracellular redox buffering systems, occurring simultaneously with modulation of expression of apoptotic molecules of the Bcl2-Bcl-XL/Bax-Bad family.

Abstract: Drug-induced acute liver failure (ALF) is a devastating and often fatal disease mainly caused by poisoning by acetaminophen (APAP). The toxic metabolite, N-acetyl-p-benzoquinone-imine (NAPQI), that leads to gluthatione depletion has been suspected to be the main effector of hepatocyte apoptosis during APAP-induced ALF. We have investigated whether reactive oxygen species (ROS) also play a role in APAP-induced ALF, and whether manganese III tetrakis (5,10,15,20 benzoic acid) (MnTBAP), a mimic of superoxide dismutase (SOD) with catalase-like activity, can treat the disease in mice. The effects of MnTBAP were tested on APAP-intoxicated mice and on isolated hepatocytes incubated with APAP. MnTBAP preventively and curatively administered significantly improved survival times, and dramatically reduced serum transaminase activity levels and parenchymal lesions in APAP-intoxicated mice. Whereas pretreatment with N-acetyl-L-cysteine (NAC) prevented ALF in a dose-dependent manner, the molecule was ineffective when curatively administered. The significant increase in glutathione peroxidase (Gpx) activity following APAP administration, and the beneficial effects of MnTBAP suggested that ROS were produced during APAP-induced ALF. A direct evidence of ROS generation was provided by flow cytometry of isolated hepatocytes incubated with APAP. In vitro, ROS production was associated with mitochondrial damage characterized by the collapse of transmembrane potential and the loss of cardiolipin content. In livers of intoxicated mice, ALF was associated with cytochrome c release that led to the activation of caspases-9 and -3. The capacity of MnTBAP to abrogate all those alterations suggests that ROS play a role in APAP-induced apoptosis of hepatocytes, and explains the beneficial effects of MnTBAP, which could be of interest in APAP-induced ALF in humans.

Abstract: BACKGROUND & AIMS: Acute liver failure (ALF) of viral origin results from massive hepatocyte apoptosis induced by the interaction between Fas expressed on hepatocytes and Fas ligand on activated T lymphocytes. Because Fas-induced apoptosis of hepatocytes involves mitochondrial damages and potential reactive oxygen species (ROS) overproduction, we investigated whether manganese III tetrakis (5,10,15,20 benzoic acid) (MnTBAP), a nonpeptidyl mimic of superoxide dismutase (SOD), can inhibit Fas-induced ALF. METHODS: An agonist anti-Fas monoclonal antibody was used to induce hepatocyte apoptosis in vitro and ALF in vivo. RESULTS: Preventive and curative treatments by MnTBAP significantly increased survival rates and significantly reduced aspartate aminotransferase levels and parenchymal lesions. ROS generation was suggested by those beneficial effects and significant increases in SOD and Gpx activities after anti-Fas injection. Flow cytometry of isolated hepatocytes incubated with anti-Fas monoclonal antibody showed that ROS production was associated with the collapse of transmembrane potential and loss of cardiolipin content. After injection of anti-Fas monoclonal antibody, mitochondrial Bcl-2 was decreased, cytochrome c released, and caspase-3 activated. Mitochondrial alterations and their consequences were abrogated by MnTBAP. CONCLUSIONS: ROS are key executioners in Fas-induced hepatocyte apoptosis. This finding explains why a nonpeptidyl mimic of SOD can cure ALF in a model of viral hepatitis, pointing out the potential interest of this molecule in humans.

Abstract: Although NO has been postulated to play important roles in host defences, it is potentially damaging for exposed cells, including for the macrophages producing the NO. Thus a network of radical acceptors and enzymes is thought to play an important redox-buffering role to protect cells against NO-mediated injury. We examined the properties of the redox systems superoxide dismutase (SOD)/catalase, glutathione (GSH) and thioredoxin (Trx), in regulating the viability of two human monocytic cell lines (THP1 and U937) exposed to the NO-generating compound diethylene triamine-nitric oxide (DETA-NO). We observed that NO-induced cytotoxic effects were time- and dose-dependent towards the two cell lines. After vitamin-induced differentiation in vitro with retinoic acid (RA) and 1,25-dihydroxy vitamin D(3) (VD), termed RA/VD, we observed that THP1 RA/VD cells became more resistant to NO-mediated cytotoxicity whereas the susceptibility of U937 cells was not modified. Using Western blotting and reverse-transcriptase PCR methods, we observed that gene transcription and protein expression of Trx and thioredoxin reductase were significantly increased upon RA/VD treatment and differentiation in THP1 cells. By contrast, SOD/catalase and GSH redox state remained unmodified. Finally, a stable transfectant THP1 line overexpressing Trx was found to be more resistant than THP1 control cells that were untransfected or transfected with an empty plasmid, when exposed to DETA-NO in vitro. In conclusion, we observed an inverse correlation between cell susceptibility to NO damaging effects and Trx expression, suggesting that the Trx system may have important preventative capacities towards NO-mediated cellular injury in monocytic macrophage cells.